nearzero.c

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/* nearzero.c: bcmath library file. */
/*
    Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
    Copyright (C) 2000 Philip A. Nelson
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
 
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.  (LICENSE)
 
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to:
 
      The Free Software Foundation, Inc.
      59 Temple Place, Suite 330
      Boston, MA 02111-1307 USA.
 
    You may contact the author by:
       e-mail:  philnelson@acm.org
      us-mail:  Philip A. Nelson
                Computer Science Department, 9062
                Western Washington University
                Bellingham, WA 98226-9062
 
*************************************************************************/
 
#include <stdbool.h>
#include "bcmath.h"
#include <stddef.h>
 
/* In some places we need to check if the number NUM is almost zero.
   Specifically, all but the last digit is 0 and the last digit is 1.
   Last digit is defined by scale. */
 
bool bc_is_near_zero(bc_num num, size_t scale)
{
    /* Error checking */
    if (scale > num->n_scale) {
        scale = num->n_scale;
    }
 
    /* Initialize */
    size_t count = num->n_len + scale;
    const char *nptr = num->n_value;
 
    /* The check */
    while ((count > 0) && (*nptr++ == 0)) {
        count--;
    }
 
    return count == 0 || (count == 1 && *--nptr == 1);
}